Antistatics



United States Patent 3,365,435 ANTISTATICS Thomas John Adams, Bound Brook, and Frank Joseph Arthen, Jr., Franklin Township, Somerset County, N.J., assignors to American Cyauamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Dec. 26, 1963, Ser. No. 333,697 5 Claims. (Cl. 260-931) This invention relates to a method for imparting antistatic properties to poly-alpha-olefinic compositions and, more particularly, to a method for the minimization of accumulated static electricity in polyolefins such as homopolymers and copolymers of ethylene and propylene. The method involves incorporating in the polyolefin a compound represented by the following Formula I:

wherein R is an alkyl radical of 7 to 16 carbons, R is H, methyl, ethyl or hydroxyethyl, alk is a straight or branched alkylene radical of 2-3 carbons, and R" is H or methyl. It relates further to the polyolefin compositions resulting from this method.

Polymeric plastic compositions typified by polyolefins (e.g., homopolymers and copolymers of ethylene, propylone and butylene) tend to accumulate surface electric charges during fabrication, and subsequently, during the life of the material. This is highly objectionable for a number of reasons. Charged bodies attract dust, and, depending upon conditions, may also give other troublesome effects such as shock to the person contacting the charged material, radio interference, etc.

Various means have been proposed to overcome or minimize the accumulation of surface electric charges including surface application of various types of anti static materials, e.g., quaternary ammonium salts. However, surface treatment is often of only temporary assistance. Application of a coating composition containing an antistatic agent, has also been proposed, but the coating processes are costly and the effect is not permanent.

It has also been proposed to incorporate the antistatic agent into the plastic composition during either compounding, molding or fabrication steps. For practical purposes, an antistatic agent for use in imparting antistatic properties to polyolefins by incorporation directly into the plastic, must fulfill certain requirements. To begin with, the agent must have sufficient antistatic activity when applied at feasible concentrations. Thus, the agent should be effective at low concentrations for reasons of economy and, in addition, to avoid impairing the properties of the polyolefinic substrate. The material must be compatible with the plastic composition and must be of such a nature that it can be easily incorporated during the conventional compounding and milling steps. The antistatic properties of the agent should be substantially permanent and should outlast exposure to high temperatures. Heat stability is especially important for use in polypropylene which must be heated to high temperatures to enable proper compounding, milling and molding thereof.

Materials have previously met certain of these require ments to varying degrees. However, there is still a definite need for a practical antistatic agent which is effective at low concentrations, has good heat stability so that its effect 3,365,435 Patented Jan. 23, 1968 is not destroyed during the fabrication or compounding steps or through the life of the material.

The present invention is based on the discovery that alkanolamines defined by Formula I meet the stated requirements for useful antistatic agents. Thus, members of this class are highly active in polyolefins at low concentrations. Whereas other agents in the past have been used at concentrations of from 1% to 5% (by weight), the new agents are effective even at concentrations of a fraction of 1%, although in some instances they may be used at concentrations as high as about 5% In addtion, they meet very stringent requirements as to heat stability, being capable of withstanding high temperatures encountered either in processing or during use, or both. Yet, they may be prepared from easily available, low-priced, starting materials.

The agents of this invention may be prepared very conveniently by the conventional reaction of a 1,2- or 2,3- epoxyalkane of 9 to 18 carbons, with an ethanol or propanolamine. In some cases, it may be desirable to react a mixture of two or more homologous epoxyalkanes, if such mixtures are available. The resulting antistatic agent will be a mixture of homologous N-hydroxyalkylethanolamines. Such agents may be employed without separation of the reaction product into its component homologs. Typical preparation will be described in the following examples.

Several methods are available for evaluation of the compounds of the invention as antistatics. Molded or extruded formulations of the polyolefins containing a known amount of the antistatic agents are prepared and these are then evaluated for heat stability, surface resistivity and presence and strength of surface static charge.

The agents of this invention can be used in the polyolefin compositions at weight concentrations of from 0.05% to 5%, preferably in the range of 0.1% to 1.0%. Either one agent may be used exclusively, or else mixtures of agents may be employed.

The invention is further illustrated by the following examples, in which parts are expressed on a weight basis.

EXAMPLE 1 N-(Z-hydroxydodecyl)ethanolamine (Agent A) 1,2-epoxydodecane (92.2 parts) and 2-aminoethanol (30.5 parts) are mixed together at room temperature in alcohol (330 parts) and refluxed two hours, then cooled. Water is added, the precipitate is filtered, and then recrystallized from aqueous alcohol. M.P. 74 C. to 76 C.

The corresponding N-propanol derivatives are prepared by the foregoing procedure using 3-aminopr0panol or isopropanolamine in place of the ethanolamine used therein.

Additional compounds are prepared using the same procedure, but other epoxyalkanes, ethanolamines and propanolamines as follows:

Agent B.Prepared by the reaction of 1,2-epoxydodecane and N-rnethylaminoethanol. The product is obtained as a liquid of B.P. l36138 C./0.l5 mm.

Agent C.Prepared by reaction of 1,2-epoxydodecane and diethanolamine. This material is a liquid of B.P. 210- 210.5 C./0.15 mm.

Agent D.-Prepared by reaction of mixed 1,2-epoxy- C C alkanes and ethanolamine. The product is a White crystalline solid. M.P. 5557 C.

Agent E.--Prepared by reaction of mixed 1,2-epoxy- C -C alkanes and ethanolamine. The product is a white crystalline solid. M.P. 60-63 0.

Agent F .Prepared by reaction of the mixed O -C epoxide and ethanolamine. The product is a white crystalline solid. M.P. 85-86 C.

Agents B, C, D, E and F have the following formulae:

4 EXAMPLE 2 Evaluation procedure and results The antistatic agents prepared as described in Example 1, and, for purposes of comparison, various other amine derivatives were evaluated as antistatic agents for polyolefins. The test methods described below, and the test results are given in Table I.

Evaluation in polyethylene and polypropylene In order to determine antistatic activity in a plastic medium, the compounds were incorporated into high density polyethylene and low density polyethylene at a 2.0% concentration and into polypropylene at 1.5%, by first milling and then compress molding the plastic into filmms which were conditioned for 24 hours at relative humidity. Antistatic activity determined by:

(1) Surface resistivity measurement (2) Cigarette ash test The sample is rubbed 20 times with a wool cloth. The distance (in inches) over which the film shows an attraction for cigarette ashes, is measured. No ash pick-up down to one inch indicates good antistatic properties.

(3) Electrostatic locator test The sample is rubbed 20 times with a wool cloth and placed one inch from the probe of the instrument. The instrument measures the magnitude of charge on the surface of the plastic. Lower values indicate good antistatic properties.

Further tests of Agent A (N-(2-hydroxydodecyl)- ethanolamine) in polyethylene and polypropylene at various lower concentrations show that antistatic properties are obtainable at concentrations as low as 0.15% in polyethylene and 0.75% concentration in polypropylene.

Results of the tests are shown in the following tables.

TABLE I.-HIGH DENSITY POLYETHYLENE l Antistatic Activity Agent (2.0 R R" R Cone.) Resis- Ash Electrotivity Test static (megohms) (inches) Locator 50x10 5. 0 500 010 21 H H 72x10 0 0 CiuHzi H CH 50x10 0. 75 CwHz H CHzCHzOH 46x10 0 25 O -n H H 28X10 0. 6 50 09-18 H H 16X10 0. 5 50 Gina H H I 25x10 0. 75 50 a Cio n H C UHBC Ei- 70x10 3. 5 300 X Phenyl H C 0H? 11- 60X10 4. 0 700 Y 01H! H C 2135(1) HC Hr- 23x10 3. 0 550 O H Z 0 H H H 40x10 3. 0 500 parison.

TABLE II.-LOW DENSITY POLYETHYLENE 2 These compounds are not part of the invention, but are included for comparison.

TABLE TIL-P OLYPROPYLENE 1 designated percent composition (2.2 parts for 0.2%, etc.) was prepared by incorporating the additive into the poly- Agent Antistafie Properties Ethylene 1:1 a B afibury mixer. The total mlxmg time was (3.0% Cone.) ve mmu es wit a maximum temperature of 380 F. Resistivity Ash Test Electrostatic 30 The charge was removed from the Banbury, calendered (megohms) (inches) Locator n the mill, cut 1nto small pieces and granulated for extrusion. The extrusion to film form was carried out as de- 1 5 500 scribed above for polypropylene, except that a tempera- 4 ture of 400 F. was used instead of 500 F.

X 1 200 70x10 0. 75 so In the following table, it 18 noted that excessive bloommg may take place at the higher concentrations. This may, however, not be objectionable for certain purposes, Melt Index 31); denslty provided the substrate is rendered antistatic.

TABLE IV.EFFECTIVENESS OF AFCIJ'ELD IIQ A IN POLYOLEFINS EXIRUDED Extrusion gggg g Resis- Eleetro- Ash Test Polymer T emp. Agent A tivity static (inches) 0.) (percent) Locator Polyethylene (low 177 0. 00 25x10 s00 10 densit 177 0.15 10 10 0 e 177 0. 25 x10 0 0 Polyethylene (high 177 0.00 Infinity 700 12 density). 177 0. 15 25x10 3 0 177 0. 25 20x10 3 0 177 0.50 Polypropylene 232 0. 00 20x10 800 10 232 0. 75 18x10 0 0 232 1.5 60x10 0 0 EXAMPLE 3 EXAMPLE 4 Polypropylene and polyethylene formulations in the form of extruded films containing Agent A of Example 1 were evaluated for antistatic properties. The test procedures were the same as those described in Example 2.

The formulations were prepared by the following procedures and the results shown in the table below.

Polypropylene-4000 parts of polypropylene, 2 parts of antioxidant (2,6di-t-butyl-p-cresol), 0.1 part of dispersant (fine particle size pyrogenic silica) and the required amount of additive for the designated percent concentration (7.5 parts for 0.75%, etc.) were mixed together and blended for 24 hours. About 10 ml. of isopropyl alcohol was added to facilitate mixing (removed prior to extrusion by drying in a steam oven at 80 C. for about 5 hours).

The samples were extruded in the form of films at 500 F.

P0lyethylene.-A composition of 1100 parts of polyethylene with the required amount of additive for the Evaluation using melt-index The melt-index, which gives a measure of the degradation of the polymer upon exposure to heat, is determined by observing the amount of polymer extruded through an orifice under a predetermined set of conditions. A higher melt-index upon exposure to heat indicates polymer degradation.

The procedure is described as follows:

A sample of polypropylene containing Agent A, the compound of Example 1, and another sample containing a commercial quaternary type antistatic agent (stearamidopropyldimethyl beta-hydroxyethylammonium nitrate) were prepared. The agents were used in a 1.5% concen tration.

An 8 gram sample of polypropylene containing the additive, prepared as described above is charged to a meltindex apparatus described in ASTM Dl23 8-62T heated at 275 C. A load of 2103 grams is applied and the extrudate which forms over a 30 second period after one 7 minute has passed, is collected and weighed. The weight of the extrudate multiplied 'by 20, is defined as the meltindex. The load is then removed and the material in the apparatus is allowed to age at 275 C. for 1.5 minutes.

comprises: a polyolefin selected from the group consisting of homopolymers and copolymers of ethylene and propylene and at least one antistatic agent of the formula:

The same load is again applied and the extrudate measf" f ured and the melt-index determined as described above. RC-CHN-alk-OH This procedure is repeated at two-minute intervals. The color of the polypropylene extrudate is also observed. The procedure is also carried out with a control sample wherein R is an alkyl group of 7 to 16 carbons, R is at having no additive. member selected from the group consisting of hydrogen, In the table below are shown the results of the determethyl and hydroxyethyl, alk is an alkylene radical of minations. 2-3 carbons, and R is a member selected from the group It may be observed that with no additive, there is a consisting of hydrogen and methyl, said compound being slight discoloration and a melt-index after 9 minutes, of present in a weight concentration of from 0.05% to 5% 22.30. The sample with the quaternized compound debased on the weight of the polyolefin. composed badly at the start, had a melt-index of 19.20 2. The composition of claim 1 wherein the polyolefin on the first determination and the experiment had to be is polyethylene. discontinued. 3. The composition of claim 1 wherein the polyolefin With the additive of Example 1, there was no appreciis polypropylene. able discoloration and a melt-index of only 17.10 was 4. The composition of claim 1 wherein the agent is reached even after 9 minutes exposure. This establishes N-(2-hydroxydodecyl)ethanolamine. that quaternary ammonium type antistatics lack heat sta- 5. The composition of claim 1 wherein the agent is a bility necessary for effective use in polyolefins. mixture of N-(Z-hydroxyalkyl)ethanolamines.

TABLE v Time of Weight of flow Extrudate MI Discoloration (minutes) Control 11.5 0.525 1050 Very light yellow.

3-3. 5 0. 705 14. 10 5-5. 5 0.815 16. 7-7. 5 0. 950 19. 00 9-9.5 1.115 22.30 Lightyellow. Commercial 1-1. 5 0.960 19. 20 Light orange (bubbles). Quat Antistatic 3-3.5 Dark brown (decomposed). AgentA 1-1.5 0. 583 11.66 Light yellow.

3-3. 5 0. 763 15. 26 5-5. 5 0. 773 15. 46 7-7. 5 0. s30 36. 60 9-9.5 0.855 17. 10 Light grey (no bubbles observed).

References Cited UNITED STATES PATENTS 5/1967 Braus 26094.9 10/1958 Brennan 260584 JOSEPH L. SCHOFER, Primary Examiner.

M. B. KURTZMAN, Assistant Examiner. 

1. A COMPOSITION HAVING ANTISTATIC PROPERTIES WHICH COMPRISES: A POLYOLEFIN SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS AND COPOLYMERS OF ETHYLENE AND PROPYLENE AND AT LEAST ONE ANTISTATIC AGENT OF THE FORMULA: 